Study of the stimulating action of sturin, its fractions, and the internal protein of T2 phage in transfection of E. coli spheroplasts by Lambda phage DNA

The stimulating action of sturin and its fractions in the transfection of E. coli spheroplasts with DNA of phage lambda has been shown, and the optimum conditions for the infection of sturin-treated spheroplasts with phage DNa have been established. The biological effect was most pronounced in arginine-enriched low-molecular sturin fraction B. The treatment of spheroplasts with the internal protein of phage T2 did not stimulate transfection. These findings suggest that the specificity of the stimulating action of protamine depends on the peculiarities of its amino acid composition, viz. a high content of arginine which is present in protein molecules in the form of blocks made up of 2-6 amino acid residues.     

Translational properties of mHNA, a messenger RNA containing anhydrohexitol nucleotides

Short messenger RNAs (mRNAs) with hexitol residues in two codons were constructed and their properties were studied in an Escherichia coli in vitro translation system. The replacement of the natural ribonucleotides of mRNA in the AUG start codon and the UUC second codon by hexitol nucleotides did not influence the main steps of translation, as indicated by the same level of binding of mRNA with or without hexitol residues under P-site conditions, and the same yield of tRNA binding to the P- and A-sites. Moreover, both peptide formation and translocation took place on mRNAs with hexitol residues. The presence of an A-type messenger hexitol nucleic acid (mHNA)-transfer RNA (tRNA) duplex is important for efficient translation and the 2'-OH function in mRNA is not necessary for binding and movement through the ribosome. Groove shape recognition of the codon-anticodon complex, more than hydrogen-bond interactions of ribose residues in mRNA, is an important factor for correct translation.     

Dissociation action of cationic peptides with hydrophobic radicals on functional coupling between serpentine type receptors and GTP-binding proteins

The coupling of hormone-activated receptor and heterotrimeric G protein is an important step of the signal transduction through adenylyl cyclase signal system (ACS). The numerous literature data and own results show that G protein-interacting regions, that are localized in cytoplasmic loops of receptors, have considerable positive charge, can form amphiphilic alpha-helices and are tightly associated with the membrane. We studied the influence of model cationic peptides on both basal and stimulated by hormones and nonhormonal agents adenylyl cyclase (AC) activity and on GTP binding activity of heterotrimeric G proteins in skeletal muscles of rats and smooth muscles of mollusc Anodonta cygnea. Peptides with hydrophobic radicals of caprinoyl acid (C10): Lys(C10)-His-Glu-Lys-Lys-(C10)-His-Glu-Lys-Lys(C10)-His-Glu-Lys-Lys(C10)- His-Glu-Lys-Ala-amide (peptide I), Cys-Lys(C10)-X-Tyr-Lys-Ala-Lys7-Trp-Lys-amide (II), Cys-X-Trp-Lys-Lys(C10)-Lys2-Lys(C10)-Lys3-Lys(C10)-Tyr-Lys-Lys(C10)-Lys-Lys- amide (III), where X--epsilon-aminocaproyl acid residue, were synthesized by solid-phase methodology. IC50 values for inhibiting the influence of peptides on serotonin-(molluscs) and isoproterenol-stimulated (rats) AC activity were: for peptide I--56 and 70 mkM, for peptide II--32 and 47 mkM, for peptide III--22 and 28 mkM, respectively. At the same time the peptides weakly decreased AC activity stimulated by nonhormonal agents (NaF, Gpp[NH]p, forskolin). Peptides I--III stimulated basal activity of the enzyme in both investigated tissues. The maximum stimulating effects (28--52%) of the peptides were observed at their concentration 10 mkM. Peptides (10--100 mkM) increased Gpp[NH]p binding in plasma membranes of mollusc and rat muscles and strongly decreased the influence of the hormones on the binding. Based on the obtained data we supposed that cationic peptides with hydrophobic radicals mimic G protein-binding regions of the receptors and can be involved in the regulation of functional coupling between the receptors and G proteins.     

SO2 污染油菜对桃蚜的影响

ＳＯ_２污染油菜对桃蚜的影响龚佩瑜,吴坤君,李秀珍（中国科学院动物研究所北京１０００８０）ＳＯ２是我国大气污染的主要成分,它是一种对生物影响很大的污染物。ｓｏ。曾被用作熏蒸剂来防治害虫,但只有在浓度很高时才有效。更多的观察表明,ｓｏ：污染有利于蚜虫的?..